1. Field of the Invention
The present invention relates to an apparatus and a method for extracting a face image required for detecting drowsy driving, and more particularly to an apparatus and a method for controlling a lens so that an image of a driver's face can be normalized to a predetermined size in the center of a monitor.
2. Description of the Related Art
In order to detect drowsy driving, a procedure of extracting images of drivers' faces must be first performed. How this procedure is performed can substantially affect the overall performance of a conventional apparatus for detecting drowsy driving. However, since the drivers may assume various driving positions and postures (e.g., the drivers may sit upright, reclined, set-back, set-forward, slouched, etc.), it is difficult to accurately detect the images of the drivers' faces. In addition, since the drivers' faces have different sizes, detecting the images of the driver's face becomes more difficult.
Images of a driver's feature photographed by the conventional apparatus for detecting drowsy driving having a fixed camera are shown in FIGS. 1(a)-1(d).
FIG. 1(a) illustrates a normal image, and FIGS. 1(b) to 1(d) illustrates abnormal images; FIG. 1(b) illustrates a case where an image is abnormal because the driver's face is photographed as a very small image; FIG. 1(c) illustrates a case where an image is abnormal because the driver's face is photographed as a very large image; and FIG. 1(d) illustrates a case where the image is abnormal because the driver's face is photographed as an image excessively-offset to the left.
When the apparatus for detecting drowsy driving is initially installed, the position for mounting the camera must be determined according to individual drivers (and their driving habits) in such a manner that the abnormal images describe above are not obtained. Although the camera is suitably mounted, driving habits may change somewhat, and/or other drivers may drive the vehicle. However, it is difficult to control the position of the camera or perform re-calibration whenever a driver's driving habit changes somewhat, and/or other drivers drive the vehicle.
The problems are caused because the conventional apparatus for detecting drowsy driving extracts the image of the driver's face by employing a fixed camera.
In addition, the apparatus for detecting drowsy driving employing a fixed camera recognizes the distance between the camera and the driver as an average distance, and an operation of extracting an area corresponding to the image of the driver's face based on the photographed image is performed through software, which increases the time required to extract an image and reduces the system's efficiency.
In addition, if the image of the driver's face is intended to be extracted from an image using the fixed camera, a normalization procedure must be performed. Although the normalization procedure is performed, information about the resolution of an input face image is always changing. Herein, the normalization procedure is required because the face area in the photographed image may have a different position or a different size due to a difference in a face's position with respect to a camera lens according to the driver's driving position.